1. Field of the Invention
The present invention generally relates to a coordinate-detecting device for detecting a position of a contact point based on voltages indicating the coordinates of the contact point, and particularly relates to a device having such a coordinate-detecting device for determining features related to an angular motion, for example, an angular displacement, an angular velocity and a number of rotations, of an operation part.
2. Description of the Related Art
Recently, information-processing devices such as personal computers and word processors are provided with improved operation systems and other improved characteristics so as to be easily manipulated by the users. Also, for such information processing devices, coordinate-detecting devices are commonly used as pointing devices rather than mouses. This is because the coordinate-detecting devices are simple to use.
However, such coordinate-detecting devices are limited to applications such as input means for the above-described information-processing device. Accordingly, there is a need for a coordinate-detecting device which can be used in a broader range of applications.
This can be achieved by adding a function for emulating a rotary encoder which can measure features related to an angular motion of an operation part, such as an angular displacement, and angular velocity and a number of rotations.
There has been a need for measuring features related to an angular motion in various applications, such as adjusting devices (e.g., a volume adjusting device, etc.) and car mount sensors. Devices actually used in the prior art are devices such as an optical rotary encoder for counting light beams passing through a slit, a magnetic rotary encoder for measuring features related to an angular motion by polarizing S and N poles, and a potentiometer of resistance-division type.
Among the above-described devices, the potentiometer of the resistance-division type has the simplest structure and is used in various fields.
The potentiometer of the resistance-division type measures an angular displacement of a contact point performing an angular motion on a resistive pad. In order to measure the angle of displacement, a constant voltage or a constant current is applied between a pair of electrodes and then a voltage at the contact point is detected. FIG. 1 is a perspective diagram showing a resistive pad 210 used in a potentiometer of a resistance-division type. The resistive pad 210 includes two sheets opposing each other with a gap between them. This structure is used as a contact surface of the pad 210. One of the sheets is provided with a resistive film 211 in a shape of a partially open ring and the other is provided with a conductive film 212. Further, the sheet provided with the resistive film 211 is provided with a pair of electrodes 213 such that the electrodes 213 are connected to the resistive film 211, respectively, at either end of the open part of the ring.
The coordinate-detecting device, which is one of the pointing devices, may be easily adapted to a graphical interface and has good operability. Therefore, such a coordinate-detecting device is now a major information input means used for a portable personal computer.
In the prior art, a coordinate-detecting device of an electromagnetic-induction type or a electrostatic-coupling type used to be major coordinate input means used for an information-processing device. However, a coordinate-detecting device of a voltage-detecting type using a resistive layer is overtaking the above-mentioned coordinate-detecting device of the prior art. This is because the coordinate-detecting device of a voltage-detecting type can detect an input with a cordless pen or a finger, has a long life, has a simple structure and is inexpensive.
The coordinate-detecting device of the voltage-detecting type using a prior-art resistive layer is provided with a coordinate input panel serving as coordinate input means. When there is an input on the coordinate input panel by a cordless pen or a finger, coordinate data is generated. The coordinate data thus obtained is used for operating a cursor based on a voltage obtained by touch on the coordinate input panel.
Further, the above-described coordinate-detecting device can recognize an input by a cordless pen or a finger as a single switch input based on the obtained voltage. In this case, the input will be sent to the information-processing device as single switch information, so as to enable operations such as an execution of a program on the information-processing device.
However, with the coordinate-detecting device of the related art, it is not possible to measure the features related to the movement of the operation part based on a voltage at a detected contact point.
The rotary encoder of the related art is capable of measuring the features related to the movement. However, for improved measuring accuracy, it is necessary to improve a pitch accuracy of the slits and a pitch accuracy of polarization. Therefore, higher mounting accuracy and edging accuracy is required for mounting components.
Also, there is a problem with the potentiometer of the resistance-division type in that accurate angle detection cannot be achieved when a contact point is on an electrode.
Therefore, there is a need for a device which can measure features relating to an angular motion without requiring high mounting accuracy and edging accuracy. Also, there is a need for a device which can carry out an accurate detection for all contact points.